Harvard Study on the Carnivore Diet

Note that this study did not objectively assess diet, nutrient status, or health-related outcomes. It should be used as a starting point for further research, not as a basis of support for the diet.

This is a review of an article published in Current Developments in Nutrition, Volume 5, Issue 12, December 2021: Behavioral Characteristics and Self-Reported Health Status among 2029 Adults Consuming a “Carnivore Diet”

The Carnivore Diet

When it comes to staying healthy, variety is key. That's the consensus among nutrition experts, who recommend that we eat a range of foods from both animal and plant sources to get all the nutrients we need. This approach has been linked to better health outcomes in studies and trials alike, and is thought to meet our dietary requirements for everything from protein to fiber.

Despite this, there are still plenty of diets out there that are focused on limiting what we eat. One of the most well-known is the vegan diet, which is often promoted for ethical, environmental, and health reasons. But while it can help with weight loss and cholesterol levels, getting all the nutrients we need from plant-based sources can also be difficult. That's where the carnivore diet comes in, which is growing in popularity as a way to cut out all plants and focus exclusively on animal foods.

While this approach has some potential benefits, like weight loss and improved mental clarity, there are also concerns about the nutritional deficiencies it can cause. Some research has suggested that a diet based solely on meat can negatively impact gut health, heart disease risk, and more. There is little data on this way of eating, but historic reports from Arctic and nomadic populations suggest that it may be possible to thrive on an animal-based diet in the long-term.

To better understand how people who follow a carnivore diet are doing in the modern world, researchers set out to study a large group of adults who were committed to this way of eating. They wanted to know more about their motivation, dietary habits, and how they felt about their health and satisfaction with the diet. While some proponents claim that a carnivore diet can provide all the essential nutrients we need, the researchers hoped to shed some light on the reality of this way of eating.

Methods

The researchers behind this study wanted to know more about the carnivore diet and the people who follow it. To gather information, they used an online survey to collect self-reported data from respondents who had been following the diet for at least six months. They asked questions about what people ate, how they felt, and what they thought of the diet. With this information, they hoped to paint a more complete picture of what it means to follow a carnivore diet.

The Boston Children's Hospital Institutional Review Board approved the study, and respondents gave their consent electronically. The only identifying data collected were email addresses, which were removed for de-identification after the survey was completed. Participants were recruited from a variety of social media communities, including Facebook, Instagram, Reddit, and Twitter. They were over the age of 18 and had been following the diet for at least six months.

Participants were recruited from a variety of social media communities, including Facebook, Instagram, Reddit, and Twitter. They were over the age of 18 and had been following the diet for at least six months.

Of the thousands of respondents who started the survey, many were excluded for various reasons, like being under the age of 18 or not having enough information to be included in the analysis. In the end, the researchers were left with a group of 2029 people who were eligible and willing to participate. While this is a large sample size, it's important to remember that it represents only a small portion of people who follow a carnivore diet.

The researchers had several goals for the survey. They wanted to characterize the diet people were following, describe how they felt about their health since starting the diet, assess whether people experienced any negative effects or symptoms of deficiencies, and evaluate how satisfied they were with the diet. To accomplish these goals, they asked a range of questions about people's food intake, health status, and perceptions of the diet. They also asked people to share any comments about the diet and how it worked for them.

It's worth noting that the survey was conducted during the COVID-19 pandemic, when many people were in lockdown. This could have had an impact on people's dietary habits and health outcomes, so it's important to keep this in mind when interpreting the results. Nonetheless, the study provides valuable insights into the motivations and experiences of people who follow a carnivore diet, and can help to inform future research in this area.

Results

When it comes to how people following a carnivore diet eat, the majority reported consuming meals 1-3 times per day, although it wasn't clear whether these were meals or snacks. The breakdown was 17% once daily, 64% twice daily, and 16% three times daily. As for what they were eating, most participants opted for meat with a high or moderate fat content, with only a small minority choosing lean cuts. Interestingly, over three-quarters of respondents reported that they preferred to eat raw, rare, or medium-rare meat. Note that consuming raw and undercooked meat brings a host of potential risk factors.

A significant portion of those following a carnivore diet reported that they were aiming to achieve nutritional ketosis, which is a state in which the body burns fat for energy instead of glucose. In fact, 41% of participants said they were trying to achieve this state, and of those, 41% monitored their ketone levels. The majority of respondents also aimed for a medium or high salt intake, which is recommended for people on low-carb diets that can lead to increased natriuresis, or the excretion of sodium in the urine.

So, how were people feeling after following the carnivore diet? According to the survey results, many reported improvements in their chronic medical conditions, general health, and well-being. They reported feeling more energetic, sleeping better, and having better mental clarity and focus. While most medical conditions improved with the diet, lipid abnormalities were not as consistent. Just over half of respondents reported that their lipid abnormalities resolved or improved, while 18% saw no change and 27% saw new occurrences or worsening of the issue. Ophthalmologic conditions were improved or unchanged with equal frequency, indicating that the diet positively impacted eye health for many respondents.

All in all, these survey results shed some light on what it's like to follow a carnivore diet and what benefits and drawbacks people may experience. While it's important to remember that this is self-reported data and that individual experiences can vary widely, the results suggest that many people who follow this way of eating are seeing positive changes in their health and well-being.

Interestingly, the respondents preferred fatty cuts of meat, and most reported eating meat at raw, rare, or medium-rare doneness. Many of them also reported wanting to achieve nutritional ketosis, and they were monitoring their ketone concentrations. When compared to low-carbohydrate diets, the findings of this study were consistent with other research, which has shown that this type of diet can result in weight loss and improved glycemic control.

Concerns and Limitations

However, there are some potential concerns related to the elimination of plant-based foods from the diet. For example, respondents reported a mixed blood lipid pattern, with LDL-cholesterol being markedly elevated while HDL-cholesterol and TG were favorable. Additionally, while the participants did not report any symptoms consistent with nutrient deficiencies, the absence of certain vitamins and minerals in their diet may have long-term effects on their health. Nonetheless, the respondents reported high levels of satisfaction with the carnivore diet and experienced little impact on their social lives or medical care.

The absence of certain vitamins and minerals in their diet may have long-term effects on their health

It's worth noting that this study is not without its limitations. It was based on self-reported data, and no objective measurements were obtained. Therefore, there may be some recall and reporting bias at play. Additionally, this study only assessed the perception of individuals following a carnivore diet and did not objectively assess diet, nutrient status, or health-related outcomes. Nonetheless, this study sheds some light on a poorly characterized dietary approach. It provides a starting point for future research into the long-term safety and benefits of a carnivore diet.

Characteristics	Responses, n	Finding, n (%) or median [IQR]	Range
Time on carnivore diet, mo	2029	14 [9–20]	6–337
Anthropometrics
Sex	2002
Male		1347 (67)
Female		651 (33)
Other		4 (0.2)
Age, y	1991	44 [34–54]	18–85
Height, cm	1818	175 [168–183]	147–203
Weight, kg	1699	76 [66–86]	38–176
BMI, kg/m2	1682	24.3 [22.1–27.0]	13.7–56.6
Sociodemographics
Country of residence	1891
United States/Canada		1205 (64)
Europe/United Kingdom		217 (11)
Australia		146 (8)
Other		323 (17)
Race		1889
White, non-Hispanic		1573 (83)
Black		16 (0.9)
Hispanic or Latino		74 (4)
Asian		59 (3)
Other		167 (9)
Education	1890
Primary or less		15 (0.8)
Secondary		179 (9)
Postsecondary		484 (26)
Tertiary		1212 (64)
Income	1888
Low		261 (14)
Middle		1244 (66)
High		383 (20)
Reproductive status (female or other)	653
Pregnant		7 (1)
Breastfeeding		10 (2)
Motivation
Aiming for ketosis	2025	832 (41)
Reason for carnivore	2029
Health/body weight		1879 (93)
Food preference		671 (33)
Curiosity		303 (15)
Ethics		185 (9)
Other		256 (13)
Health reasons	1879
Body weight/composition		1572 (84)
Athletic performance		869 (46)
Focus/energy		1398 (74)
Allergies/skin/autoimmunity		1131 (60)
Digestive health		969 (52)
Mental health		848 (45)
Diabetes		232 (12)
Other		297 (16)